The nasal airway (NA) is responsible for warming, humidifying, and cleansing a significant portion of inhaled air. Consequently, it is the first part of the respiratory tract to be exposed to the harmful effects of gases and particles. Inhalation experiments using human volunteers show a very large (30 percent) range in particle dose delivered to the NA- a variation that propagates throughout the remainder of the respiratory tract and consequently leads to significant uncertainty in measuring, for example, the medicinal dose received by a patient. No theoretical model exists that can explain the large inhaled dose uncertainty or to predict accurately the gas the particle dose filtered by the NA. Issues concerning particle inhalation are serious; epidemiological studies show that one in four Americans die from a respiratory disease. A better understanding of particle deposition in the airway can be realized by developing an accurate experimental description of particle deposition. The first step toward this goal is the mapping of the anatomical features of the human NA that influence particle deposition. Charge Coupled Device (CCD) imaging technology is being developed by this investigator to locate fluorescing particles deposited in a full-scale multi- section replica of a human NA. The CCD measures local particle deposition patterns for different sized particles at different steady-state flow rates as follows. Fluorescent images of each section of the model, taken with a CCD camera, are combined to form three-dimensional particle deposition patterns. Parts of the model will be exchanged with similar NA sections from a library of digitized NA's from sixty human subjects. These systematic studies will determine both how variations in NA geometries affect particle deposition and what fraction of the inhaled particles is deposited at each specific area in the NA.